Thick-pasting starch containing ureaformaldehyde and process of making the same



T. POROWSKI 2,838,465 THICK-PASTING STARCH CONTAINING UREA-FORMALDEHYDEJune 10, 1958 AND PROCESS OF MAKING THE SAME 4 Sheets-Sheet 2 Filed June1 8, 1957 gfix mfib hv Qw mm mm mm on E Q m 85% Wi EMMS QNREL mmfi kmu RH Q Q NEE I smgbawmuua qfigm EQN R E S w m 8 5 0M W MM 09A T m Qm mT 9QQNN June 10, 1958 T. POROWSKI 3 THICK-PASTING STARCH CONTAININGUREA-FORMALDEHYDE AND PROCESS OF MAKING THE SAME Filed June 18, 1957 4Sheets-Sheet 3 mmmg UNQNN Q ow Q Q .3 om Q 9 m INVENTOR. T/zadaewP0f0ZZ/5/6Z/,

June 10, 1958 T. POROWSKI 2,838,465

THICK-PASTING STARCH CONTAINING UREA-FORMALDEHYDE AND PROCESS OF MAKINGTHE SAME Filed June 18, 1957 4 Sheets-Sheet 4 b 5w ow hm mm mm QM 9 2 mU m Q m W m N fi m nm NQ Q A 1% B &3 ism Q \M w w wfi ks EQ Q \wQ a W kEmu @w 8 MQQ Q oW QM AWv 1M, A 4 T B 8. A w w 32% Q 8m W 4 M W on m'II-lICK-PASTENG STARCH CONTAINING UREA- FDRMALDEHYDE AND PROCESS OFMAKING THE SAME Thaddeus horowslni, Wheaten, 111., assignor to A. E.Staley Manufacturing Company, Decatur, Ill., a corporation of DelawareApplication June 13, 1957, Serial No. 666,807

11 Claims. (Cl. 260-173) This invention relates, generally toimprovements and innovations in starch to be used for preparingthickened starch paste. More particularly, the invention relates to themanufacture of a thick-pasting starch characterized by its ability tocook rapidly to form a high viscosity paste which will retain itsviscosity at a relatively stable level at high temperatures.

This application is a continuation-in-part of my prior applicationSerial No. 433,377, filed June 1, 1954, now abandoned.

In Patent No. 2,407,071, dated September 3, 1946, a method of making athick-pasting starch is disclosed which involves reacting native starchwith dimethylol urea at a pH in the range of l;7.0, adjusting the pH ofthe reaction medium within the range of 4.5-7.0 if not already in thatrange, and then filtering and drying.

While thick-pasting starch may be manufactured satisfactorily accordingto the procedure disclosed in Patent No. 2,407,071, it has beendiscovered in accordance with the present invention that an improvedthick-pasting starch product may be obtained by departing significantlyfrom the process disclosed in Patent No. 2,407,071, making use ofunobvious innovations.

While the disclosure of Patent No. 2,407,071 indicates that thestarch-resin reaction may be carried out in a broad pH range of 1.58, ithas been found in practicing the present invention that, preferably, thepH of the reaction medium should be in the range of from 3 to 5.Furthermore, whereas, Patent No. 2,407,071 teaches that after thereaction the pH of the medium should be adjusted to 4.57.0 beforefiltering, it was discovered according to the present invention that thereacted starch-resin medium should be made alkaline before it isfiltered and dried. Usually there is no advantage in adjusting the pHvalue of the starch-resin medium higher than 10. When these innovationsare followed, the resulting thiclcpasting starch has the ability to cookrapidly to a high viscosity in either alkaline tap water, distilledwater or acid Water, and to retain this viscosity at a fairly stablelevel at high temperatures.

Accordingly, the object of the present invention, generally stated, isthe provision of an improved thickpasting starch product and a method ofmaking the same.

An object of the present invention is the provision of a thick-pastingstarch product characterized by its ability to cook rapidly and equallywell in Water at paste pH values ranging from about 4 to and form a highviscosity paste which has excellent hot viscosity stability forprolonged periods of time.

Another object of the invention is a method of preparing athicl'epasting product having the foregoing characteristics by reactingunmodified starch and a small amount of a water-soluble, heat-reactiveureaformaldehyde composition including monomethyl urea (MMU) anddimethylol urea (DMU).

Certain other objects of the invention will, in part, be obvious andwill, in part, appear hereinafter.

For a more complete understanding of the nature atet and scope of theinvention, reference may now be had to the following detaileddescription thereof taken in conjunction with the accompanying drawingswherein Figs. 1-4 are viscosity temperature curves which serve to bringout more clearly the nature and advantages of applicants invention. Eachof these figures will be described below.

The general procedure for preparing the novel and improved thick-pastingstarch products in accordance with this invention is briefly as follows:Unmodified starch is slurried in water and the urea formaldehydecomposition (e. g. DMU) is added in a proportion of 0.05-0.15 based onthe dry weight of the starch. It is desirable to dissolve the DMU inalkaline Water so as to prevent resinification before it is added to thestarch. This also increases the rate of solubility of the DMU. The Watermay be made alkaline with a small amount of lime or disodium phosphate.Preferred proportions of the urea formaldehyde composition are from0.07-O.1%. The concentration of the'starch slurry is not critical butpreferably should be kept in the range of about 18 to 22 B. in order tominimize the bulk to be handled and filtered. The pH of the slurry isadjusted as required to a pH of from 3 to 5. This reaction medium isthen heated to a temperature substantially below the gelatinizingtemperature of the starch, a temperature in the range of about 120 F.being satisfactory. While the reaction will proceed at a temperature aslow as room temperature (i. e. 70 F.), the rate is much slower andtherefore it is normally desirable to heat the reaction medium.Preferably the medium is stirred during the reaction sutficiently topromote a uniform reaction. After the reaction is sufiiciently complete(e. g. l4 hours) it is made alkaline up to a pH of about 10, a pH of 8being very satisfactory, by addition of soda ash, caustic soda or othersuitable alkaline reagent. The alkaline reaction medium is then filteredand dried.

The following examples are illustrative presently preferred embodimentsof the invention:

Example 1 A single-washed starch slurry was used containing 40 parts byweight of unmodified corn starch and 60 parts of Water and having 'a pHof 4.1. 0.03 parts by Weight of dimethylol urea (Du Pont Arboneeld A)was dissolved in 0.15 parts of water made alkaline tolitmus by theaddition of a small amount of disodium phosphane. The solution ofdimethylol urea was added to the starch slurry. The temperature of thereaction medium was maintained at 100 F. and a mechanical agitator wasused to stir the reaction medium. After 2 hours the pH of the reactedmedium was adjusted to 7.5 by the addition of sodium carbonate and thenit was filtered and the filter cake washed and dried. The resultingproduct was in dry granular form and cooked rapidly in water to form athick paste which maintained its viscosity at a stable level for 4 hours(i. e. the end of the test). This thick paste may be used inapplications where increased viscosity over that produced .by the nativestarch is desired, e. g. adhesives for use in making paperboard andpaper bags and in ore flotation. The Scott viscosity of the unreactedstarch used in this example was 82 and the thick-pasting starch-DMUreaction product had a Scott viscosity of 341. The Scott test is arecognized procedure for determining viscosity. (See Kerr-Chemistry andIndustry of Starch, page 11-9, 2nd edition.)

Example 2 A slurry was used containing 40 parts by weight of native cornstarch and 60 parts of water and having a pH of 4.0. There was added tothe starch slurry a solution containing 0.05 parts by weight ofmonomethylol urea (Du Pont Arboneeld B) and 0.2 part by weight of Water.The reaction mixture was heated to 105 F. and held at that temperaturefor 2 hours, using mechanical agitation. The pH was adjusted to 7.5 withsodium carbonate and the reaction mixture was filtered. The filter cakewas washed and then dried. The resulting dry product cooked rapidly inwater to form a thick paste which retained its viscosity at a stablelevel while remaining at 207 F. for several hours. The Scott viscosityof the hot paste was 308. The star-ch paste so produced is useful forthe purposes pointed out in Example 1.

Example 3 A slurry was used containing 40 parts by weight of native cornstarch and 60 parts of water. 0.04 parts by weight of a water-solubleurea-formaldehyde resin (American Cyanamid Co. Urac 180) was dissolvedin 0.1 part of water. The solution of urea-formaldehyde resin was addedto the starch slurry and suflicient hydrochloric acid was added toadjust the slurry to 4.3 pH. The tem perature of the reaction medium wasraised to 105 F. and the reaction'medium was stirred by a mechanicalagitator. After 2 hours the reaction medium was adjusted to 7.5 pH bythe addition of sodium carbonate, and then it was filtered. The filtercake was washed and dried. The resulting dry product cooked rapidly inwater to form a thick paste which retained its viscosity at a stablelevel for several hours (until the end of the test) at 207 F. The Scottviscosity of unreacted native starch was 60. The Scott viscosity of thethick-pasting starch-resin reaction product was 279. The starch paste soproduced is useful for the purposes pointed out in Example 1.

While unmodified, native starches in general may be made intothick-pasting starch in accordance with the present invention, theinvention is particularly useful in connection with corn starch both byreason of its commercial importance and by reason of the large increasein viscosity which may be obtained.

The nature of the invention is further brought out in connection withthe curves contained in the drawings wherein viscosity-timerelationships for starch-DMU re action products are plotted. In Fig. 1curve 1 was obtained with a starch-DMU reaction product wherein0.07%'dimethylol urea was reacted with native corn starch at pH 4.1 andthe starch-DMU reaction product was dried and recovered without a finalpH adjustment. Curve 2 was obtained with a starch-DMU reaction prod uctobtained by reacting 0.07% dimethylol urea with corn starch at a pH of4.1 and with an adjustment of the pH to 7.5 before filtering and drying.Curve 3 represents a control based on the starch alone with nodimethylol urea being used.

In obtaining the curves, 50 grams of the dry substance were dispersedinto 950 grams of tap Water having a pH of 8.1. The Corn IndustriesResearch Foundation (CIRF) Viscometer was used which is a continuoustype viscosimeter which records on a chart the cooking history of starchdispersed in water. The viscosity is recorded directly on the chart interms of gram-centimeters torque.

The curves in Fig. 1 bring out that the thick-pasting starch-resinreaction products prepared in accordance with the present invention(curve 2) cooks rapidly in alkaline tap water to a high stable viscositywhile the products obtained without final adjustment of the pH to analkaline value before drying (i. e. curve I) cooked very slowly, even ata rate below that of native, unmodified starch itself (i. e. curve 3).

In Fig. 2 the curves correspond generally to those contained in Fig. 1but were obtained by cooking the starch samples in distilled water asdistinguished from alkaline tap water. In Fig. 2 curves 1, 2 and 3 wereobtained by cooking 50 grams of corresponding dry samples in 950 gramsof distilled water. These curves again clearly bring out that thestarch-resin product prepared in accordance with the present invention,wherein the reaction product is made alkaline before filtering, cooksrapidly in distilled water to a high viscosity which remains stable fora long period of time. Curve 1 of Fig. 2 shows that when thestarch-resin reaction product was not made alkaline before filtering anddrying, it did not yield a paste the viscosity of which was heat stable,even though it reached a higher peak viscosity than the starchresinproduct obtained in accordance with the present invention (i. 0. curve2).

Fig. 3 contains curves showing the same relationship between the threestarch samples when they are cooked in slightly acid water as whencooked in distilled water.

Fig. 4 contains five curves showing hot paste viscosities of fivestarch-DMN reaction products obtained by reacting 0.075% of DMU withunmodified corn starch at a pH of 4.1 after which the pH of five sampleswas adjusted to 7.5, 8.0, 8.5, 9.0 and 9.5 respectively, beforefiltering and drying. It will be seen that the viscosity of the 7.5 pHsample remains practically level (i. e. constant) whereas the higher pHvalue samples have an increased tendency to have peak values and thenfall oil. On this basis, it appears unnecessary and undesirable toadjust to an alkaline pH above 10.

Having fully described my invention, what is claimed as new is:

1. A process of preparing a starch product characterized by its abilityto cook rapidly in an aqueous medium to form high viscosity starchpastes which are stable at high temperatures which comprises, reactingat an acid pH and at a temperature of at least F. but substantiallybelow the pasting temperature of the starch an aqueous slurry ofunmodified starch with from about ODS-0.15% of at least onewater-soluble, heat-reactive, urea-formaldehyde composition selectedfrom the group consisting of dimethylol urea, monomethylol urea, andwater-soluble urea-formaldehyde resin, based on the weight of the starchin said slurry, adjusting the pH of the reacted medium to an alkaline pHranging up to about 10, and recovering the starch-resin reaction productfrom the alkaline medium.

2. A thick-pasting starch-resin reaction product prepared in accordancewith the process of claim 1.

3. A starch paste prepared by cooking in water a thick-pastingstarch-resin reaction product prepared in accordance with the process ofclaim 1.

4. A process of preparing thick-pasting starch which is relativelynon-sensitive to pH and cooks rapidly in water to form a high viscositypaste having excellent heat stability, comprising, reacting at a pH offrom about 3-5 and at an elevated temperature substantially below thepasting temperature of the starch an aqueous slurry of unmodified starchcontaining from about 0.05-0.l5% of at least one water-soluble,heat-reactive, urea-formaldehyde composition selected from the groupconsisting of dimethylol urea, monomethylol urea, and water-solubleurea-formaldehyde resin, based on the dry weight of the starch,adjusting the pH of the reacted medium to an alkaline pH ranging up to10 and recovering the starchresin reaction product from the alkalinemedium.

5. The process of claim 4 wherein the urea-formaldehyde composition isdissolved in alkaline water before it is mixed with the starch slurry.

6. The process of claim 4 wherein the starch-resin reaction product isrecovered by filtering the alkaline reaction medium and drying thefilter cake.

7. The process of claim 4 wherein the reaction time is from 14 hours andthe reaction temperature is from about -120 F.

8. A thick-pasting starch-dimethylol urea reaction product prepared inaccordance with the process of claim 4.

9. The process of claim 4 wherein the unmodified starch is corn starch.

10. A thick-pasting starch-resin reaction product prepared in accordancewith the process of claim 9.

11. A process of preparing thick-pasting starch which is relativelynon-sensitive to pH and cooks rapidly in water to form a high viscositypaste having excellent heat stability, comprising, reacting at a pH offrom about 3-5 and at an elevated temperature substantially below thepasting temperature of the starch an aqueous slurry of native starchcontaining from about ODS-0.15% of dimethylol urea based on the dryweight of the starch, adjusting the pH of the reacted medium to analkaline pH ranging up to 10 and recovering the starch- 5 resin reactionproduct from the alkaline medium.

No references cited.

1. A PROCESS OF PREPARING A STARCH PRODUCT CHARACTERIZED BY ITS ABILITY TO COOK RAPIDLY IN AN AQUEOUS MEDIUM TO FORM HIGH VISCOSITY STARCH PASTES WHICH ARE STABLE AT HIGH TEMPERATURES WHICH COMPRISES, REACTING AT AN ACID PH AND AT A TEMPERATURE OF AT LEAST 70*F. BUT SUBSTANTIALLY BELOW THE PASTING TEMPERATURE OF THE STARCH AN AQUEOUS SLURRY OF UNMODIFIED STARCH WITH FROM ABOUT 0.50-0.15% OF AT LEAST ONE WATER-SOLUBLE, HEAT-REACTIVE, UREA-FORMALDEHYDE COMPOSITION UREA, MONOMETHYLOL UREA, AND WATER-SOLUBLE UREA-FORMALDEHYDE RESIN, BASED ON THE WEIGHT OF THE STARCH IN SAID SLURRY, ADJUSTING THE PH OF THE REACTED MEDIUM TO AN ALKALINE PH RANGING UP TO ABOUT 10, AND RECOVERING THE STARCH-RESIN REACTION PRODUCT FROM THE ALKALINE MEDIUM. 